Assessment of left ventricular contraction with LV Emax during cardiopulmonary bypass in patients with open heart surgery

: There are few reports on the assessment of left ventricular contraction during cardiopulmonary bypass (CPB) in open heart surgery. LV Emax is thought to be a load-independent index of left ventricular function. We used a left ventricular conductance catheter to measure LV Emax from "non-working beating heart" during CPB in 16 patients who underwent open heart surgery. During CPB, at 45 minutes after aortic declamping, changes of heart rate with atrial pacing (120/min) did not change LV Emax, but after intravenous dobutamine administration (DOB, 10 micrograms/kg/min) LV Emax increased by 26% (p < 0.01). DOB increased LV Emax in 14 of 16 patients during CPB. These 14 patients were weaned from CPB without difficulty. But in 2 other patients DOB didn't increase LV Emax during CPB. In order to be weaned from CPB, the two patients needed epinephrine and intraaortic balloon pumping. We concluded that change of LV Emax made by intravenous administration of dobutamine is one of useful indexes to assess left ventricular contractility during cardiopulmonary bypass.